GIRLS!!! Please answer. Advice?

Okay so,i really like this girl and shes in choir for school masses and I play guitar for them, im really good. Anyways im 16 and so is she and I know for a fact we both love john mayer. The place I take guitar lessons at has teen open mics. She has an amazing voice and I was wondering if her and I can do a duet or some john mayer covers together at an open mic. Heres the catch we always make eye contact and I catch her looking at me a lot and vice a versa. But im uber shy and dont know how I should approach her. Shes cute and I think Im decent looking (you can check my yahoo pulse). Anyways how can I ask her. And last semester we had a clas together so I cant introduce myself. And why does she look at me?